“That will always trump the number of people who leave their cars at home because of high fuel prices.

“Many drivers will use their cars because they are paying for them anyway, rather than take another form of transport.”

Gavin Booth, senior officer for Scotland for watchdog body Bus Users UK, said northern Scotland had seen the biggest fall in passengers because services were less frequent and more prone to cuts in council funding.

Liberal Democrat transport spokesman Jim Hume said: “Times are tight at the moment for bus companies with the rising cost of fuel and operating costs, and the SNP are doing nothing to help bus companies.

“The SNP have landed a blow on bus companies with a cut to the bus operators’ grant.”

A Transport Scotland spokeswoman said: “A number of factors are likely to have impacted on bus patronage in recent years, not least the two unprecedentedly bad winters, challenging economic conditions, and effective use of smartcard technology to combat fraudulent use of concessionary travel entitlements.

“It is simply untrue to say this government has reduced funding for local bus services over this period.”

She said it had increased by 7 per cent between 2007-8 and 2010-11, with total support for the industry of £250 million a year.